Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the lingual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars.
Mature calculus consists of an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to bone, enamel, and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris, and various types of microorganisms.
As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. This is undesirable from an aesthetic standpoint.
Mechanical removal of calculus periodically by the dentist is routine dental office procedure. A variety of chemical and biological agents have also been suggested to retard calculus formation or to remove calculus after it is formed. Pyrophosphate salts are chemical agents known to have the ability to retard calculus formation as described, for example, in U.S. Pat. No. 4,999,184, to Parran, Jr. et al., issued Mar. 12, 1991, the disclosure of which is incorporated herein by reference in its entirety.
In addition to the pyrophosphate salts, other polyphosphates are also know to help retard calculus formation. U.S. Pat. No. 4,627,977, issued Dec. 9, 1986, to Gaffar et al. discloses the use of linear molecularly dehydrated polyphosphate salts combined with a fluoride ion-providing source and a synthetic linear polymeric polycarboxylate which inhibit enzymatic hydrolysis of the polyphosphate salt in saliva. U.S. Pat. No. 4,247,526, to Jarvis et al., issued Jan. 27, 1981, discloses the use of a pharmaceutically acceptable condensed phosphate salt in addition to dicalcium phosphate dihydrate and trimagnesium phosphate. Although polyphosphate containing oral care products are known, there is a continuing need to develop stable products containing polyphosphates.
The present inventors have discovered that certain polyphosphates, in particular, linear polyphosphates with average chain lengths greater than 4 will significantly react with most ionic fluoride sources in oral compositions and alter the pH of the oral compositions. This reaction compromises the ability of the oral composition to provide stable ionic fluoride and polyphosphate to the oral surfaces. The inventors have discovered that the polyphosphates do not react with monofluorophosphate, under normal manufacturing, storage, and use conditions. Therefore, in a single phase dentifrice composition, monofluorophosphate a suitable fluoride ion source to be present with the polyphosphate and still deliver a constant and similar source/amount of fluoride.
Therefore, it is an object of the present invention to provide stable single phase oral compositions comprising monofluorophosphate and polyphosphates. It is also an object of the present invention to provide oral compositions with improved antitartar activity through the use of polyphosphates.
These and other objects of the present invention will become readily apparent from the detailed description which follows.
All percentages and ratios used herein are by weight of the oral composition, unless otherwise specified. All measurements are made at 25.degree. C., unless otherwise specified.